The present invention relates generally to an electronic circuit board device. More particularly, the present invention is concerned with a resin coated electric circuit board device.
In a manufacturing process of an electric circuit board device, several basic devices are arranged on the surface of a base plate. The electric circuit board device comprises, for example, resistors, condensers, relays, integrated circuits (IC) or other electric devices. To provide the electric circuit board device with reliability, a coating of resin material is applied to the surface of the base plate. The resin coating is prepared for the electric circuit board device as a final manufacturing process. A gap is provided between the surface of the base plate and the electric devices. In the resin coating process, a blow-hole may occur in the resin material. The blow-hole does not prevent the entry of humidity between the base plate and the devices.
In order to prevent the entry of humidity, one consideration is proposed in Japanese laid-open publication, No. 60(1985)-165789. The characteristic features of the prior art disclosure are as follows:
Step 1: Electric devices are provided on the base plate with solder connections;
Step 2: Coating material is stored in a container having an ultrasonic generator; and
Step 3: Ultrasonic vibrations are applied to the coating material so that the coating material spreads uniformly into the gap wherein blow-holes are removed from the gap.
The largest technical defect in this related art is applying the ultrasonic vibration to the electric device. Due to such vibrations, the growth of a crack may be generated on the surface of the base plate or the wiring pattern and the crack may lead to rupture of the device.